1. FIELD OF INVENTION
This invention relates to a guide wire for a catheter for making the catheter guidable, and more paticularly to a guide wire for a catheter for making the catheter for the medical treatment or tests introducible to a predetermined position in a blood vessel, digestive duct, trachea, other body cavities or the like and retainable thereat.
2. DESCRIPTION OF THE PRIOR ART
Heretofore, as a guide wire for a catheter, there has been used a coil-shaped guide wire formed of a stainless steel wire, a piano wire or a monofilament-shaped guide wire made of plastics. Each of the above-mentioned guide wires of the prior art incorporates a general metallic material such as a stainless steel wire or piano wire progressively being reduced in sectional area from a body portion to a distal end portion thereof in a portion or over the total length of its interior, whereby the guide wire is formed of the body portion comparatively high in rigidity and the distal end portion comparatively flexible.
As typified in the case of retaining the Angiographic Catheter at a predetermined position in a blood vessel, in many cases, the aforesaid guide wire is percutaneusly inserted into the blood vessel by use of an introducing needle, the distal tip opening portion of the catheter is covered onto a proximal end portion of the guide wire disposed outside of a human body, and the catheter is inserted into the blood vessel with the guide wire being utilized as an arbor. Therefore, a certain level of rigidity is given to the body portion of the aforesaid catheter so that the guide wire is made smoothly insertable into the blood vessel against a resistance generated between the outer surface of the guide wire and the tissues of the human body and the catheter is made guidable against a resistance generated between the outer surface of the guide wire and the inner surface of the catheter.
However, as described above, since the body portion of the conventional guide wire is made of the general metallic material and plastic deformation is caused to the body portion when a certain value of displacement is exceeded, the guide wire may be buckled depending on the skill in manual operation, whereby the buckled portion may be turned into an unrestorable deformed portion, and this deformed portion forms a considerable obstruction against the advance of the catheter, so that difficulties are felt for an operation of smoothly introducing the catheter. Furthermore, in the case of guiding the catheter by previously curving the distal end portion of the catheter so that the catheter can be readily inserted into the predetermined position in the blood vessel, the catheter is covered onto the guide wire and comes into the state of being straightened. Hence, the resistance of the catheter covered onto the guide wire is increased, whereby a possibility of occurrence of a trouble caused by the aforesaid buckling is increased.
In order to have the catheter reach the predetermined position of the blood vessel after the catheter together with the guide wire has been inserted into the blood vessel, it is necessary to further advance in the blood vessel the distal end portion of the guide wire projected a predetermined length from the distal end opening of the catheter. Therefore, the distal end portion of the conventional guide wire needs to have such a flexibility that the guide wire does not damage the wall of a blood vessel, adapts itself to the shape of a meandering blood vessel, and is insertable into a complex vascular branching.
However, as described above, since the distal end portion of the conventional guide wire is made of a general metallic material or plastics, plastic deformation is caused to the distal end portion when a certain value of displacement is exceeded, whereby the flexible movability of the guide wire for reaching a predetermined position in the blood vessel is endangered. Furthermore, even if the distal end portion of the guide wire reaches the predetermined position in the blood vessel, the distal end portion is lowered in its rebound due to plastic deformation. Hence, while the forward end portion of the catheter is being advanced, there is no resistance between the distal end portion of the guide wire and the wall of blood vessel, which is required for retaining the forward end portion of the guide wire against the flexure stress of the catheter, with the result that the distal end portion of the guide wire is drawn out of the predetermined position of the blood vessel. And, in many cases, the retention of the guide wire at the predetermined position ends in a failure and much time is wasted for the manual operation. There has been proposed a guide wire, the distal end portion of which is previously deformed into a J-shape so as to prevent the wall of blood vessel from being damaged and the distal end portion of the guide wire from engaging the wall of the blood vessel during its movement in the blood vessel. However, the distal end portion of the guide wire of the type described never fails to be deformed into a rectilinear shape while it passes through the introducing needle. Hence, thereafter, the distal end portion of the guide wire is not restored to a perfect J-shape, and, in many cases, such a disadvantage is presented that the initial function is not satisfactorily fulfilled.
Furthermore, it is preferable that the above-described guide-wire has the outer diameter substantially equal to the inner diameter of the catheter, so that the catheter thus guided can expand the wall of skin and the wall of blood vessel naturally and smoothly. As for the distal end portion of the guide wire, it is preferable that, to prevent the blood from leaking out through a gap formed between the introducing needle and the guide wire when the guide wire is inserted into the introducing needle, the distal end portion has the outer diameter substantially equal to the inner diameter of the introducing needle, i.e., the outer diameter of the body portion of the guide wire. Therefore, in the above-described guide wire, it is preferable that the outer diameter of the guide wire is made substantially equal to the inner diameter of the distal end portion of the catheter to guide the guide wire, whereby, even if the outer diameter of the guide wire is increased, both the body portion and the distal end portion can be provided with the elastic strain characteristics required, respectively.
One object of the present invention is to provide a guide wire for a catheter making the catheter reliably and readily introducible to a predetermined position.
More specifically, such object is to provide a guide wire capable of avoiding buckling when the body portion of the guide wire is inserted and covered by the manual operation.
Another object of the present invention is to provide a guide wire capable of being restored to the original state, even if the guide wire buckles, and not affecting the insertion and the covering.
A further object of the present invention is to provide a guide wire having the distal end portion flexible enough to be insertable, even when a complicated vascular system is encountered, and a good restoring force against deformation.
A still further object of the present invention is to provide a guide wire having the distal end portion, which constantly has a suitable rebound and may be retained at a predetermined position when it guides the catheter.
A yet further object of the present invention is to provide guide wires of various outer diameters, having the physical properties substantially identical with one another.